Not Applicable.
Not Applicable.
Not Applicable.
1. Field of the Invention
The present invention relates generally to hard copy apparatus, more particularly to print media sensing, and specifically to an optical sensing method and apparatus for print media sheet recognition.
2. Description of Related Art
In designing paper path for hard copy apparatus, a designer must address the problem of detecting print media (hereinafter referred to generically as xe2x80x9cpaper,xe2x80x9d regardless of form, e.g., plain paper, special media, envelopes, and the like as would be common to the state of the art), including type recognition, positioning, multiple sheet picks, and transport to and through the printing zone.
Clearly, knowledge of the type of media currently being printed is an obvious necessity.
Other related printing problems also exist. For example, it is rare that multiple sheet picks present perfectly registered sheets of paper where a printing errorxe2x80x94generally print registration on the pagexe2x80x94will not occur. When multiple sheets are overlapped, state of the art paper length sensing devices generally indicate a single sheet that is longer than the actual media in the input supply because the commonly used optical detectors or opto-mechanical interrupters inherently do not have the capability to sense the presence of two overlapped sheets of paper since the overlapped region between the two sheets generates the same signal as a single sheet.
Exemplary optical media sensing methods and apparatus are shown in U.S. Pat. No. 5,135,321 (Olsen et al.), U.S. Pat. No. 5,466,079 (Quintana) and its divisional, U.S. Pat. No. 5,564,848 (each assigned to the common assignee herein and incorporated by reference in their entireties). Multiple sheet picks effect a throughput loss as any print is likely to be mis-registered, requiring a reprinting.
Another ADVANCED MEDIA DETERMINATION SYSTEM FOR INKJET PRINTING is described by Walker et al. in U.S. patent application Ser. No. 09/607,206 (a continuation-in-part of Ser. No. 09/430,489, which is a continuation-in-part of Ser. No. 09/183,086, which is a continuation-in-part of U.S. Pat. No. 6,036,298 (incorporated herein by reference). A system of classifying the type of incoming media entering an inkjet or other printing mechanism is provided to identify the media without requiring any special manufacturer markings. The leading edge of the incoming media is optically scanned using a blue-violet light to obtain both diffuse and specular reflectance values. A Fourier transform of these reflectance values generates a spatial frequency signature for the incoming media. The spatial frequency is compared with known values for different types of media to classify the incoming media according to major categories, such as transparencies, glossy photo media, premium paper and plain paper, as well as specific types of media within these categories, such as matte photo premium media and highloss photo media. An optimum print mode is selected according to the determined media type to automatically generate outstanding images without unnecessary user intervention. A printing mechanism constructed to implement this method is also provided.
U.S. patent application Ser. No. 09/470,812 by Barbera et al. for a METHOD AND APPARATUS FOR PRINT MEDIA DETECTION (assigned to the common assignee herein and incorporated by reference) describes a multi-purpose, transmissive paper sensor which includes a light beam projector and light detector having an analog output signal. Changes in the output signal from an open loop condition indicate the presences of at least one print medium being in the field-of-view of the sensor. Output signals indicative of print media leading edge, trailing edge, and number of sheets interrupting the light beam provide improved print media transport control for hard copy apparatus.
It has been determined that there are additional criteria by which media can be characterized.
In accordance with the present invention, media thickness and transmissivity are used to increase media detection accuracy. Additionally, the present invention can be used to determine if there has been a multi-pick at the input supply.
In its basic aspect, the present invention provides a method for identifying an unknown print medium, the method including: recording data representative of medium thickness and transmissivity using an incident light source; and comparing recorded data from said recording to predetermined data representative of known print medium thickness and transmissivity,
In another aspect, the present invention is a method for characterizing print media including: beaming transmissive light through a first type of print medium; impinging the light onto surface reflective of the light and a surface absorptive of the light; recording a profile representative of light reflection and light absorption; and storing said profile in a memory with an identifier associated with said first type of print medium.
In another aspect, the present invention provides a method for determining a multi-pick feed of cut sheet print media, the method including: storing first data representative of media thickness and transmissivity of a single in sheet of a known print medium; storing second data representative of media thickness and transmissivity of at least two stacked sheets of a known print medium; recording third data representative of current medium thickness and transmissivity during transport of said current medium from a supply toward a printing zone; and comparing said third data to said first and second data.
In yet another aspect, the present invention provides a print media sensor device, including: mounted for bracketing a print media transport path, emitterxe2x80x94receptor means for directing a light beam across the transport path, the light beam having predetermined intensity and wavelength for penetrating print media; and aligned with the emitter means such that said light beam is received after passing through a sheet of print media in said path, an associated light absorbing means and an associated light reflecting means for receiving the light beam, wherein the receptor means provides an output signal indicative of thickness and transmissivity of the sheet.
In still another aspect, the present invention is a computer memory including: computer code for recording data representative of print medium thickness and transmissivity using an incident light source; and computer code for comparing recorded data from said recording to predetermined data representative of known print medium thickness and transmissivity.
The foregoing summary is not intended to be an inclusive list of all the aspects, objects, advantages and features of the present invention nor should any limitation on the scope of the invention be implied therefrom. This Summary is provided in accordance with the mandate of 37 C.F.R. 1.73 and M.P.E.P. 608.01 (d) merely to apprise the public, and more especially those interested in the particular art to which the invention relates, of the nature of the invention in order to be of assistance in aiding ready understanding of the patent in future searches. Other objects, features and advantages of the present invention will become apparent upon consideration of the following explanation and the accompanying drawings, in which like reference designations represent like features throughout the drawings.